RF domains

ABSTRACT

A wireless access point broadcasts a unique RF domain identifier for each supported service set per radio. Within a wireless local area network (“WLAN”) the RF domain identifier is unique for each supported service set, and hence identifies the service set. In addition to identifying the service sets supported by the access point, RF domain identifiers may be used to adjust transmit power in order to differentiate service sets. For example, if a first access point receives a beacon with an RF domain identifier transmitted by a second access point, the transmit power of communications associated with the service set associated with the received RF domain identifier is reduced at the first access point if that service set is also supported on the same radio by the first access point. In one embodiment the first and second access points both reduce transmit power until the beacons are no longer received by the respective nearby access point. The transmit power of communications associated with other service sets and other radios are not effected by the transmit power reduction, i.e., the access point may reduce transmit power of overlapping service set communications while contemporaneously transmitting communications of non-overlapping service sets at full power.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a reissue of U.S. Pat. No. 7,773,944, issued on Aug.10, 2010, which issued from U.S. patent application Ser. No. 11/145,712,filed on Jun. 6, 2005, the contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

This invention is generally related to wireless communications, and moreparticularly to identifying and differentiating service sets supportedby RF access devices.

BACKGROUND OF THE INVENTION

One way in which wireless local area networks (“WLANs”) are employed isto provide communications services in device-dense environments andbuildings that inhibit communication with wider area wirelesstechnologies such as cellular phone networks. A cellular phone networkmay employ towers capable of communicating with a wireless device at arange of up to approximately 20 km. Within a particular segment ofspectrum each tower is capable of supporting communications with afinite number of wireless devices. Because of inter-tower interferencethere are limits to the number of cell towers that can be deployed insupport of a device-dense area such as a shopping mall, airport orsports stadium. The problem is exacerbated when the device-dense area ispartially shielded from RF communications with the towers. WLAN accesspoints, in contrast with typical cellular network towers, generally havea shorter range, operate at lower power levels, are less expensive, andare relatively small in size. Hence, multiple WLAN access points may bedeployed within the device-dense area in order to provide improvedsupport for wireless communications. However, it is desirable to provideimproved WLAN support for mobile services in device-dense environments.

SUMMARY OF THE INVENTION

This invention is predicated in-part on recognition that it is desirableto advertise support for multiple service sets by a single wirelessaccess point. The invention is also predicated in-part on recognitionthat it may be desirable to differentiate service sets supported byaccess points in a WLAN.

In accordance with the invention, an apparatus such as a radio frequency(“RF”) access point which provides at least one service set to a clientdevice is operable to broadcast a RF domain identifier associated withthe service set. The RF domain identifier is unique for each supportedservice set per radio within a wireless local area network (“WLAN”),where each radio is defined by a set of frequencies and a modulationtechnique, and wherein each access point may support multiple differentradios. The RF domain identifier may be included in a beacon which isperiodically broadcast. Consequently, a recipient of the beacon canidentify a service set supported by the access point from the RF domainidentifier.

In addition to identifying the service set supported by the accesspoint, RF domain identifiers may be used to adjust transmit power inorder to differentiate service sets. For example, if a first accesspoint receives a beacon with a RF domain identifier transmitted by asecond access point, the transmit power of communications associatedwith the service set associated with the received RF domain identifieris reduced at the first access point if that service set is alsosupported by the first access point. In one embodiment the first andsecond access points both reduce transmit power until the beacons are nolonger received by the respective nearby access point. The transmitpower of communications associated with other service sets are noteffected by the transmit power reduction. In particular, the accesspoint may transmit communications of the overlapping service set atreduced power while contemporaneously transmitting communications ofnon-overlapping service set at full power. Transmit power reduction mayalso be triggered by service set priority, i.e., a lower priorityservice set may be subjected to reduce transmit power because a higherpriority, different service set is being provided on the same channel.

Those skilled in the art will recognize that a Service Set Identifier(“SSID”) might be used to identify service sets. The SSID is a sequenceof up to 32 alphanumeric characters or numbers defined by IEEE standard.However, the SSID is typically employed to broadcast the name of theWLAN rather than the name of a service set. Consequently, identificationof multiple service sets with SSIDs might conflict with the typical useof the SSID. Further, network administrators sometimes suppress SSIDbroadcasts because the SSID can be employed to connect with the WLAN,and hence is a potential security vulnerability. For these reasons theRF domain identifier is superior to the SSID for the purpose of serviceset identification and differentiation.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a WLAN in which RF domains are broadcast to indicateservice sets supported by particular access points.

FIG. 2 illustrates a RF domain identifier field.

FIG. 3 illustrates a method of employing RF domains to enhance provisionof wireless communications services.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless local area network (“WLAN”) for supportingservice set identification and differentiation in device-denseenvironments. The WLAN includes access points (100), (102), (104), whichare in wired communication with a network (106) such as the internet viaa switch (108). The access points are located at fixed positions withinthe environment, and function to provide wireless access to clientdevices (110), (112). In particular, a wireless client deviceestablishes a link with one of the access points within communicationsrange, and the access point transmits data between the device and thenetwork via the switch. The wireless device is typically mobile, and mayroam between access points.

Each access point supports at least one communications service set. Aservice set may include all service types provided by a communicationsservice provider, a subset of service types provided by the serviceprovider, a particular service type associated with a service provider,or at least one service type provided by multiple communications serviceproviders. Examples of service types include, but are certainly notlimited to, voice, video, data, Internet access, and LAN access toapplications which support transactions associated with the device-denseenvironment such as purchasing and reserving goods and services. Itshould therefore be apparent that an access point could support thevoice services of multiple, different service providers. Similarly, theaccess point could support multiple levels of data service from a singleservice provider. Further, the access point could support multipleservice sets on different radios, e.g., on IEEE 802.11b and 802.11g.

Referring to FIGS. 1 and 2, the access points (100-104) are configuredto advertise support of particular service sets. In particular, theaccess points use a unique radio frequency (“RF”) domain identifier(200) per radio for each supported service set. The RF domainidentifiers in the illustrated example each include a 16-character fieldthat can be used to identify a service set by name. For example, the RFdomain identifier could be the name of a service provider. The RF domainidentifier is broadcast by the access points in conjunction withcommunications associated with that service set. In the illustratedexample access point (100) is broadcasting a beacon (114) indicatingsupport of a particular service set associated with RF domain A.Consequently, RF domain identifier A is included in that beacon (114).Access point (102) also supports the service set associated with RFdomain identifier A, and hence includes RF domain identifier A in abeacon (116). Access point (102) also supports the service setassociated with RF domain identifier B which is broadcast in beacon(118). Access point (104) supports the service set associated with RFdomain identifier C, which is included in beacon (120).

The RF domain identifiers are also employed to set transmit powerlevels. Because RF domain identifier B and RF domain identifier Cservice sets are not supported by other nearby access points, beacon(120) and beacon (118) are broadcast at full power. However, becauseaccess points (100) and (102) support the same service set associatedwith RF domain identifier A, service set differentiation is implementedby adjusting transmission characteristics based at least in-part on theRF domain identifiers received via the beacons. When access point (100)receives a beacon (116) indicating support of a service set that is alsosupported on the same channel by that access point, i.e., the RF domainidentifier A service set, then a power adjustment routine is executed.The power adjustment routine, which is executed by both access points(100 and 102) causes the transmit power to be reduced until beacon (116)is not received by access point (100), and beacon (114) is not receivedby access point (102).

It should be noted that if access points (100) and (102) support thesame service set associated with RF domain identifier A but on differentradios then service set differentiation is not necessarily implemented.In particular, when access point (100) receives a beacon (116)indicating support of a service set that is also supported by thataccess point but on a different radio then the support is considered tobe non-overlapping. Non-overlapping support of a service set does nottrigger adjustment of transmit power levels.

Because a single access point may support multiple service sets andmultiple radios, a single access point may broadcast a separate beaconfor each supported service set per radio, i.e., a separate beacon foreach RF domain identifier. In the illustrated example access point (102)is broadcasting beacon (118) indicating support of the RF domainidentifier B service set at full power while contemporaneouslybroadcasting beacon (116) indicating support of the RF domain identifierA service set at reduced power. Further, the communications associatedwith support of those service sets are transmitted at the same powerlevel as the beacon. Hence, access point (102) supports the RF domainidentifier service set A only within the range of beacon (116), whilesupporting the RF domain identifier B service set within the range ofbeacon (118).

Referring now to FIGS. 1 and 3, while various transmission poweradjustment routines could be utilized, in the illustrated embodiment theaccess point is operable to execute the power adjustment routinedescribed in U.S. patent application Ser. No. 10/780,843 entitledWIRELESS ACCESS POINT PROTOCOL METHOD, filed Feb. 18, 2004 (published asU.S. Patent Application Publication No. 2005/0026611), which isincorporated herein by reference. Initially, access point (100)transmits at maximum power. Once access point (100) has successfullyclaimed the channel it determines whether another access point isoperating on the same channel as indicated by step (300). If anotheraccess point is operating on the channel, e.g., access point (102), adetermination is made whether there is an intersection between theservice set it is supporting and the service set advertised by thebeacons it receives as indicated in step (302). If the nearby accesspoint (102) is broadcasting a beacon (116) advertising an intersectingservice set, e.g., RF domain identifier A on the same radio, then accesspoint (100) calculates a transmit power (“TP”) backoff value and adjustsits transmit power for data transmissions associated with that serviceset downward to facilitate overall RF domain identifier A service setthroughput in the WLAN as indicated in step (304). The power adjustmentroutine is contemporaneously adjusted by both access points (100, 102),provided both access points receive the beacons from one-another, untiltransmission power is decreased to a point at which the beacons are nolonger received. The access points may maintain tables which identifynearby access points and variables such as a Max TP backoff value tofacilitate power adjustment.

The power adjustment routine may also be triggered based on service setpriority. For example, if access point (102) receives a beacon (120)from access point (104), the beacon (120) is examined to determine theservice set that is being advertised, e.g., RF domain identifier C.Access point (102) then determines from a table maintained in memorywhether any of the service sets supported by access point (102) on thesame channel with the same radio have a lower priority than RF domainidentifier C. The transmit power of each lower priority service set isreduced to a level calculated to not reach access point (120). Thecalculation may be facilitated by including an indicator of transmitpower level in beacon (120). The difference between the indicatedtransmit power level in the beacon (120) and the actual power level ofthe beacon as received at access point (102) provides an indication ofthe transmit power level at which communications will reach access point(104).

While the invention is described through the above exemplaryembodiments, it will be understood by those of ordinary skill in the artthat modification to and variation of the illustrated embodiments may bemade without departing from the inventive concepts herein disclosed.Moreover, while the preferred embodiments are described in connectionwith various illustrative structures, one skilled in the art willrecognize that the system may be embodied using a variety of specificstructures. Accordingly, the invention should not be viewed as limitedexcept by the scope and spirit of the appended claims.

What is claimed is:
 1. Apparatus for providing radio frequency (“RF”)access in support of at least one service to a client device,comprising: a receiver operable to receive communications from theclient device and to receive an RF domain identifier transmitted byanother device; processing logic operable to determine whether theservice associated with the received RF domain identifier has a higherpriority than supported services, and to reduce transmit power ofcommunications associated with supported services having lower prioritythan the service associated with the received RF domain identifier; anda transmitter operable to transmit communications to the client device,the transmitter being further operable to support multiple services, andto transmit an RF domain identifier associated with each supportedservice, wherein the supported service includes at least one of: allservice types provided by a communications service provider; a subset ofservice types provided by the service provider; a particular servicetype associated with a service provider; and at least one service typeprovided by multiple communications service providers; and wherein theservice types include at least one of voice, video, data, Internetaccess, and local area network (“LAN”) access to applications.
 2. Theapparatus of claim 1 wherein the transmitter is further operable totransmit a unique RF domain identifier for each supported service perradio.
 3. The apparatus of claim 1 wherein the RF domain identifier isincluded in a beacon.
 4. The apparatus of claim 1 further includingprocessing logic operable to reduce transmit power of communicationsassociated with a service following detection of overlapping support forthe service by the other device.
 5. The apparatus of claim 4 whereincommunications associated with two different services are transmitted atdifferent power levels.
 6. The apparatus of claim 1 further includingprocessing logic operable to transmit communications associated with asupported service having lower priority at a relatively lower power thana service having a relatively higher priority.
 7. A method for providingradio frequency (“RF”) access in support of at least one service to aclient device, comprising: receiving communications from the clientdevice; transmitting communications to the client device; supportingmultiple services by broadcasting an RF domain identifier associatedwith each supported service, wherein the supported service includes atleast one of: all service types provided by a communications serviceprovider; a subset of service types provided by the service provider; aparticular service type associated with a service provider; and at leastone service type provided by multiple communications service providers;and wherein the service types include at least one of voice, video,data, Internet access, and local area network (“LAN”) access toapplications; and receiving an RF domain identifier transmitted byanother device; and determining whether the service associated with thereceived RF domain identifier has a higher priority than supportedservices; and reducing transmit power of communications associated withsupported services having lower priority than the service associatedwith the received RF domain identifier.
 8. The method of claim 7 furtherincluding the step of broadcasting a unique RF domain identifier perradio for each supported service.
 9. The method of claim 7 wherein theRF domain identifier is included in a beacon.
 10. The method of claim 7further including the step of reducing transmit power of communicationsassociated with the service associated with the received RF domainidentifier, provided that service is supported via the same radio, i.e.,service support overlaps.
 11. The method of claim 10 further includingthe step of transmitting at different power levels communicationsassociated with two different services.
 12. The method of claim 7further including the step of reducing transmit power of communicationsassociated with supported services having lower priority than theservice associated with the received RF domain identifier.
 13. Themethod of claim 7 wherein transmit power of communications associatedwith supported services having equal or higher priority than the serviceassociated with the received RF domain identifier are not reduced.
 14. Awireless access point comprising: a transmitter configured to transmit asignal containing an identification of at least one service offered bythe wireless access point; and a receiver configured to receive from atleast one other wireless access point at least one signal containing anidentification of at least one service offered by the at least one otherwireless access point; wherein the wireless access point is configured:to determine whether a received identification of at least one serviceoffered by the at least one other wireless access point identifies atleast one service also offered by the wireless access point, and, toreduce a power level to be used by the transmitter to transmit at leastsignals associated with the at least one service also offered by thewireless access point, in the case where it is determined that thereceived identification of at least one service offered by the at leastone other wireless access point identifies at least one service alsooffered by the wireless access point.
 15. The wireless access point ofclaim 14, wherein the transmitter is configured to transmit a beaconcontaining the identification of at least one service offered by thewireless access point.
 16. The wireless access point of claim 14,wherein the identification of at least one service offered by thewireless access point comprises a name of a service provider offeringthe at least one service.
 17. The wireless access point of claim 14,wherein the wireless access point in configured to reduce the powerlevel to be used by the transmitter to transmit at least signalsassociated with the at least one service also offered by the wirelessaccess point by calculating a transmit power backoff value.
 18. Thewireless access point of claim 14, wherein the transmitter includesmultiple radio transmitters supporting multiple communication channels.19. The wireless access point of claim 18, wherein the wireless accesspoint is configured to reduce a power level to be used by thetransmitter to transmit at least signals associated with the at leastone service also offered by the wireless access point by calculating atransmit power level such that a beacon being transmitted for theservice will not be received by the at least one other wireless accesspoint.
 20. The wireless access point of claim 19, wherein thecalculating includes computing a difference between a received powerlevel and an indicated transmit power level of the at least one signalreceived from the at least one other wireless access point.
 21. A methodof wireless communication, comprising: transmitting, by a wirelessaccess point, a signal containing an identification of at least oneservice offered by the wireless access point; receiving, at the wirelessaccess point, at least one signal from at least one other wirelessaccess point, wherein the at least one signal contains an identificationof at least one service offered by the at least one other wirelessaccess point; determining whether at least one receive identification ofat least one service offered by the at least one other wireless accesspoint identifies at least one service also offered by the wirelessaccess point; and reducing a transmit power level to be used fortransmitting at least signals associated with the at least one servicealso offered by the wireless access point, in the case where the atleast one receive identification of at least one service offered by theat least one other wireless access point identifies at least one servicealso offered by the wireless access point.
 22. The method of claim 21,wherein said transmitting includes transmitting a beacon containing theidentification of at least one service offered by the wireless accesspoint.
 23. The method of claim 21, wherein the identification of atleast one service offered by the wireless access point comprises a nameof a service provider offering the at least one service.
 24. The methodof claim 21, wherein said reducing the transmit power to be used fortransmitting at least signals associated with the at least one servicealso offered by the wireless access point includes calculating atransmit power backoff value.
 25. The method of claim 21, wherein saidreducing the transmit power to be used for transmitting at least signalsassociated with the at least one service also offered by the wirelessaccess point comprises calculating a transmit power level such that abeacon being transmitted for the service will not be received by the atleast one other wireless access point.
 26. The method of claim 25,wherein the calculating includes computing a difference between areceived power level and an indicated transmit power level of the atleast one signal received from the at least one other wireless accesspoint.
 27. A non-transitory computer-readable storage medium containinginstructions for execution by a processing apparatus of a wirelessaccess point, wherein the instructions are configured to result in theimplementation of operations comprising: transmitting a signalcontaining an identification of at least one service offered by thewireless access point; receiving at least one signal from at least oneother wireless access point, wherein the at least one signal contains anidentification of at least one service offered by the at least one otherwireless access point; determining whether at least one receiveidentification of at least one service offered by the at least one otherwireless access point identifies at least one service also offered bythe wireless access point; and reducing a transmit power level to beused for transmitting at least signals associated with the at least oneservice also offered by the wireless access point, in the case where theat least one receive identification of at least one service offered bythe at least one other wireless access point identifies at least oneservice also offered by the wireless access point.
 28. The medium ofclaim 27, wherein said transmitting includes transmitting a beaconcontaining the identification of at least one service offered by thewireless access point.
 29. The medium of claim 27, wherein theidentification of at least one service offered by the wireless accesspoint comprises a name of a service provider offering the at least oneservice.
 30. The medium of claim 27, wherein said reducing the transmitpower to be used for transmitting at least signals associated with theat least one service also offered by the wireless access point includescalculating a transmit power backoff value.
 31. The medium of claim 27,wherein said reducing the transmit power to be used for transmitting atleast signals associated with the at least one service also offered bythe wireless access point comprises calculating a transmit power levelsuch that a beacon being transmitted for the service will not bereceived by the at least one other wireless access point.
 32. The mediumof claim 31, wherein the calculating includes computing a differencebetween a received power level and an indicated transmit power level ofthe at least one signal received from the at least one other wirelessaccess point.